Sensitizers for photographic emulsions



United States Patent 3,006,762 SENSITIZERS FOR PHOTOGRAPHIC EMULSIONS Fritz Dersch, Binghamton, N.Y., assignor to General Aniline & Film Corporation, New York, N.Y., a corporation of Delaware No Drawing. Filed Feb. 9, 195), Ser. No. 791,849 Claims. (Cl. 96107) This invention relates to a novel sensitizer for use with light-sensitive silver halide emulsions. More particularly, this invention relates to the use of poly-N-vinyl- 2-oxazolidone as a sensitizer for photographic silver halide emulsions.

It is well known that compounds such as the polyalkylene oxides and certain derivatives hereof increase the speed of silver halide emulsions. These sensitizers, however, have a tendency to increase the formation of fog during storage of the photographic film, especially during storage at elevated temperatures and humidities.

It is an object of this invention to provide a photographic silver halide emulsion having a novel sensitizer associated therewith which increases the speed of the emulsion and produces an increase in density upon a given exposure.

It is a further object of this invention to provide a photographic film having an emulsion layer thereon containing a novel sensitizer and wherein the tendency of the emulsion to fog is minimized.

A still further object of this invention is to provide a photographic silver halide emulsion containing poly- N'vinyl-2-oxazolidone as a sensitizer.

Other objects and advantages of this invention will appear to those skilled in the art from the detailed description thereof given below.

I have discovered that poly-N-vinyl-Z-oxazolidone has a remarkable speed increasing effect on silver halide emulsions and produces an increase in density for a given exposure.

Poly-N-vinyl-Z-oxazolidone, prepared according to US. Patent 2,818,362, is a long chain compound having the following general chemical formula:

L in wherein n depicts the number of N-vinyl-2-oxazolidone groups, which are members of the high molecular chain, n being at least 80 and as high as 4,000 or more.

The increase of eflFective sensitivity of photographic silver halide emulsions with poly-N-vinyl-Z-oxazolidone can be obtained in a number of ways. ltmay be added to an undercoating, to a middle coating, to an overcoating or to a surface coating prior to the coating operation. If desired, it may be added during the actual preparation of the emulsion either before or after washing of the emulsion.

The sensitivity increasing agent of my invention may be used in various types of photographic emulsions, e.g., non-sensitized emulsions, orthochromatic, panchromatic and X-ray emulsions. If used with sensitizing dyes, it may be added to the emulsion before or after the dyes are added. Various silver salts may be used in forming the light-sensitive emulsion such as silver bromide, silver iodide, silver chloride or mixed silver halides. The poly- N-vinyl-Z-oxazolidone may be used in emulsions intended for color photography, e.g., emulsions containing colorforming components. The carrier in the photographic emulsion may be gelatin or other colloids such as collodion, albumen, cellulose derivatives, polyvinyl alcohol or 3,006,762 Patented Oct. 31, 1961 synthetic resins. The emulsion containing my novel sensitizer may be coated on any conventional base, such as paper, glass, cellulose ester such as cellulose acetate, cellulose others and others.

The following specific examples are given of the manner of producing emulsions containing the novel sensitizing agent of my invention. It is to be understood, however, that these examples are given by way of illustration and not by way of limitation.

Example I A silver halide emulsion in gelatin containing 4% silver iodide and 96% silver bromide was prepared in a conventional manner and brought up to its maximum light-sensitivity. It was then readied for coating on film base, that is, melted at 40 C. Necessary coating finals were added such as sensitizing dyes, stabilizers and hardeners. A 25% aqueous solution of poly-N-vinyl-Z-oxazolidone having an average molecular weight of about 40,000 was prepared and the following quantities added to samples of the above described emulsion, each containing about 0.4 mol of silver halide. The so prepared emulsion samples were coated on a suitable cellulose ester base and dried. Samples of these film coatings were then exposed in a type IIB Sensitometer and developed in a developer of the following composition:

Water to make 1.0 liter.

The results obtained were as follows:

Quantity of Poly- N-vinyl-Q-oxazo- Relative lidone Added, g. Speed 14 Fog Example II A silver halide emulsion in gelatin containing 4% silver iodide and 96% silver bromide was coated on film base in a manner known to the art. After the coating was performed, an aqueous gelatin solution containing 20 grams of gelatin per liter and 2 grams of poly-N-vinyl-Z- oxazolidone of an average molecular weight of about 160,000 was coated thereon as an antiabrasion layer. After drying, film samples were exposed and processed as described in Example I. The samples described exhibited a relative speed of 115 and a fog of .2 as compared with a type coating of the same emulsion having an antiabrasion layer similar to that described above but lacking the poly-N-vinyl-2-oxazolidone and having a speed of 80 and a fog of .2.

My invention is not limited to the detailed description contained herein, but includes all modifications that fall within the scope of the appended claims.

I claim:

1. A photographic material comprising a base having a light-sensitive organic colloid silver halide emulsion thereon, such material additionally containing poly-N- vinyl-Z-oxazolidone to increase the sensitivity of said emulsion, said poly-N-vinyl-Z-oxazolidone having at least eighty N-vinyl-2oxazolidone groups in the molecular chain.

2. A light-sensitive organic colloid silver halide emulsion containing, in addition to the colloid, poly-N-vinyl- 2-oxazolidone as a sensitizer therefor, said poly-N-vinyl- 2-oxazolidone having at least eighty N-vinyl-Z-oxazolidone groups in the molecular chain.

3. A photographic material comprising a base, a layer of gelatino-silver halide emulsion thereon, said emulsion containing as a sensitizer, poly-N-vinyl-Z-oxazolidone having at least eighty N-vinyl-Z-oxazolidone groups in the 7 molecular chain.

4 5. A photographic material comprising a'base, a layer of a light-sensitive organic colloid silver halide emulsion on said base, said layer being overcoated with another layer comprising poly-N-vinyl-Z-oxazolidone having at least eighty N-vinyl-2-oXazolidone groups in the molecular chain.

References Cited in the file of this patent UNITED STATES PATENTS 2,818,362 Drechsel Dec. 31, 1957 FOREIGN PATENTS 687,751 Great Britain Feb. 18, 1933 

1. A PHOTOGRAPHIC MATERIAL COMPRISING A BASE HAVING A LIGHT-SENSITIVE ORGANIC COLLOID SILVER HALIDE EMULSION THEREON, SUCH MATERIAL ADDITIONALLY CONTAINING POLY-NVINYL-2-OXAZOLIDONE TO INCREASE THE SENSITIVITY OF SAID EMULSION, SAID POLY-N-VINYL-2-OXAZOLIDONE HAVING AT LEAST EIGHTY N-VINYL-2-OXAZOLIDONE GROUPS IN THE MOLECULAR CHAIN. 